Duvet Inner bad quality

I’m disappointed in the quality of Volpes duvet inners. I purchased a duvet Inner (Super King) and after receiving it, we washed it, following the washing instructions as labelled. Do not dry clean, do not tumble dry, wash in cold water etc. After washing and wanting to make the bed,we noticed that the duvet had shrunk by at least 20%. Due to Volpes returns policy, where they do not take returns of duvet inners,I am unable to replace it. Very disappointed.